Crosstalk in headsets is an unwanted phenomenon in which a sound played in one stereo channel is also heard in the other channel. All stereo and multichannel audio equipment suffer from varying degrees of crosstalk. Crosstalk in audio transmission applications is normally declared in specifications of audio performance parameters, such as frequency response, distortion, etc. Audio transmission applications have varying degrees of sensitivity to crosstalk (e.g., crosstalk in these applications may have different distortion effects and/or perceptibility). For example, three-dimensional (3D) audio with audio filtered by head related transfer functions requires low crosstalk.
Crosstalk in headsets arises mainly due to the wiring of the headphones. The wiring in audio headsets includes a common ground lead that connects both ear speakers to the input/output jack. There are impedances in all the leads, so that an applied voltage (i.e., a music signal) is divided over the resistances in the leaders and the speaker element. The part of the signal separated by the common ground impedance is heard in the second channel because the common ground is directly fed to the second ear speaker. Crosstalk may be reduced in headsets by specifying a maximum allowed impedance in the leads and in the input/output jack (e.g., a 3.5 mm connector).